Typically, a mattress comprises a spring core or so-called spring assembly covered on the top and bottom sides by a cushioning pad and encased with an upholstery covering. The spring core is generally comprised of a matrix of coil springs laced together in the top and bottom planes of the springs and surrounded by top and bottom border wires. Additionally, the mattress may have border or edge support springs mounted between the top and bottom border wires to provide additional stiffness or support around the outer border of the mattress. Additionally, one or more handles may be provided on each of opposing sides of the mattress cover to facilitate movement of the mattress.
In normal use, the mattress and coil springs are subjected to increased local loading along the borders of the mattress, which tends to diminish not only the appearance of the mattress, but also the comfort it may provide. For example, sitting on the edge of the bed will depress the top border wire to the point, in time, where it may acquire a permanent deformation. Furthermore, this deformation may result in an uncomfortable tilting or sloping of the bed to one side resulting in a tendency for one lying on the mattress to roll to the low side of the bed.
Border reinforcing springs or edge support springs have been developed in various forms to support the edges of mattresses. However, a common problem with these edge supports is that the edge support spring structures can be relatively "loose" so that movement of the edge supports results in undesirable noise. The noise which results from the use of edge support springs is a result of the fact that the torsional members of the edge support which provide the resilient support are not secured tightly together along their entire length. This enables the torsional members to slip relative to one another during use thereby generating the undesirable noise associated with known edge support springs.
U.S. Pat. No. 5,370,373 describes an edge support spring, commonly referred to in the art as a torsional "fishmouth-shaped" edge support, designed to alleviate the above described problems. The edge support spring comprises a pair of torsional wires, each formed of a length of wire bent to have an elongated center section and transverse arms that extend perpendicular to the elongated center section. The end portions of the transverse arms extend outwardly and are secured to the top and bottom border wires by means of a helical border wire. The center sections of the two torsional wires are also bound to each other by means of a helical lacing wire to prevent translational (longitudinal and lateral) movement relative to one another. U.S. Pat. No. 3,200,417 discloses a similar two torsional spring structure with the difference being that the center sections are bound together with clips rather than helical lacing wires. These two torsional structures permit rotational movement of the transverse arms, such that the center portions pivot relative to one another when a load is applied to the mattress. This provides a "soft firmness," but it is still desirable to provide customers with a line of mattresses having firmer edge support.
The nature of mattress manufacturing is that mattress spring cores, or so-called spring assemblies, are generally manufactured in one facility and then shipped to a second facility where the cores are covered and upholstered. In the course of upholstering the spring core of the mattress at the second facility, accessories such as these edge support springs may be added to the standard core so as to differentiate mattress models or styles. Mattress upholsterers customarily do not have the equipment or the capabilities of the mattress core manufacturer. Therefore, the assembly and installation of the edge support springs must be done with a minimal amount of effort, expertise, or equipment. The two torsional spring structures discussed above have the disadvantage of requiring the second facility to join the torsion wires to each other as well as join each to a border wire. Thus, it is desirable develop edge support springs that limit the effort, expertise, and equipment needed for assembling the mattress.
It is also customary in the manufacture of mattresses to provide handles extending through the cover of the mattress to enable the mattress to be conveniently lifted, moved and turned. These handles typically include a grippable member that extends along the outer surface of the cover on the side of the mattress and a pair of end portions that extend into the mattress through openings in the cover. As described in U.S. Pat. Nos. 5,214,810 and 3,590,405, for example, the end portions are secured to the coil springs through the use of a connecting wire or rod that extends through corresponding turns of the springs. While it is desirable to direct the strain from pulling the handle away from the cover of the mattress, this design has the disadvantage of concentrating the strain on the central convolutions of selected outermost coil springs of the mattress.
Great Britain published patent application No. 2,168,250 describes a mattress configuration having a continuous length of edge support wire to which a handle is attached. The edge support wire is of an undulating or wavy construction so as to provide laterally extending upper sections connected to an upper border wire, laterally extending lower sections connected to a lower border wire and intermediate sections extending obliquely between the upper and lower sections. Periodically around the perimeter of the mattress, the intermediate section further comprises a laterally extending section. The handles are described as being attached to these laterally extending sections. This takes the strain off the inner coil springs and redirects it to the edge support wire. While this edge support wire provides vertical and horizontal support to the mattress and the inner coil springs, it provides less resiliency than the fishmouth-shaped edge support springs.
There is thus a need to provide an edge support configuration that is easy to assemble, that provides a high degree of firmness while retaining some degree of resiliency, and that is adapted to receive a handle such that the amount of strain on the internal springs and on the cover is minimized or eliminated.